The present invention relates to an infrared heater which emits a warm gaseous fluid, such as warm air, and more particularly to an infrared heater which emits a warm gaseous fluid together with far-infrared rays having a wave length of 3 .mu.m or longer for use in effecting reflowing of solder, curing of resins, drying of food, heating of wood and wet coatings, warming for medical treatment, and the like.
Recently, there is a general trend for electronic equipment to be made increasingly compact and lightweight. Accordingly, printed circuit boards having a large number of electronic parts mounted in a limited area (hereunder referred to as "high-density boards" or "high-density printed circuit boards") are widely used. In the manufacture of high-density boards, it is necessary to supply heat to a narrow area between electronic parts on the high-density board in order to reflow a paste solder or cure an adhesive resin when the electronic parts are connected to the circuit board using a paste solder or a resinous bonding agent. As an industrial heating apparatus for these purposes, a reflow furnace is used in which infrared heaters are placed on the top and bottom walls of a tunnel-type heating zone. The infrared heater used in the reflow furnace comprises a sheath heater, or else a simple heater supported by a steel plate. The wave length of the emitted radiation is not longer than 3 .mu.m.
Since infrared rays travel in straight lines, the electronic parts on the high-density board prevent the infrared rays from directly reaching the areas where solder or adhesive resin was previously placed. Thus, sometimes the reflowing of a paste solder or the curing of a bonding agent is not sufficient to effect bonding of the electronic parts to the circuit board.